12 research outputs found
Multi-wavelength observations of multiple eruptions of the recurrent nova M31N 2008-12a
We report the optical, UV, and soft X-ray observations of the
eruptions of the recurrent nova M31N 2008-12a. We infer a steady decrease in
the accretion rate over the years based on the inter-eruption recurrence
period. We find a ``cusp'' feature in the and band light curves close
to the peak, which could be associated to jets. Spectral modelling indicates a
mass ejection of 10 to 10 M during each eruption, and
an enhanced Helium abundance of He/He 3. The super-soft
source (SSS) phase shows significant variability, which is anti-correlated to
the UV emission, indicating a common origin. The variability could be due to
the reformation of the accretion disk. A comparison of the accretion rate with
different models on the plane yields the mass of a CO
WD, powering the ``H-shell flashes'' every 1 year to be
M and growing with time, making M31N 2008-12a a strong candidate for
the single degenerate scenario of Type Ia supernovae progenitor.Comment: Submitted to AJ, 22 pages, 14 figures, 5 table
Measurements of the deuteron and proton magnetic form factors at large momentum transfers
Measurements of the deuteron elastic magnetic structure function B(Q\u27) are reported at squared four-momentum transfer values 1.20~ Qi ~ 2.77 (GeV/c)\u27. Also reported are values for the proton magnetic form factor Gstr(Q2) at 11 Q values between 0.49 and 1.75 (GeV/c) . The data were obtained using an electron beam of 0.5 to 1.3 GeV. Electrons backscattered near 180\u27 were detected in coincidence with deuterons or protons recoiling near 0 in a large solid-angle double-arm spectrometer system. The data for B(Q ) are found to decrease rapidly from Q =1.2 to 2 (GeV/c), and then rise to a secondary maximum around Q\u27=2. 5 (GeV/c)\u27. Reasonable agreement is found with several different models, including those in the relativistic impulse approximation, nonrelativistic calculations that include meson-exchange currents, isobar configurations, and six-quark configurations, and one calculation based on the Skyrme model. All calculations are very sensitive to the choice of deuteron wave function and nucleon form factor parametrization. The data for GMr(Q\u27) are in good agreement with the empirical dipole fit